Female cuckoo calls are more effective at attracting breeding male cuckoos and their hosts than male cuckoo calls

This study was done in Sifangtuozi Farm. The Sifangtuozi Farm (46°00′-46°22′ N, 123°46′-123°57′ E) is located in Zhenlai County, in the Nenjiang River basin, a tributary of the Songhua River, in the northeastern Jilin Province, China. The area is characterized by abundant water resources, and extensive stands of cattails and reeds can be found in various areas surrounding the farm, including field dikes, irrigation channels, streams, and ponds. Every breeding season (May-August), many individuals of the Oriental reed warbler (Acrocephalus orientalis, ORW) and black-browed reed warbler (Acrocephalus bistrigiceps, BRW) migrate to these wetlands to breed (Trnka et al., 2023). ORWs are the primary hosts of CCs in Asia. In northern China, the parasitism rate of the CCs can reach as high as 34.3% to 65.5% (Yang et al., 2016, 2017).There have been numerous studies on the calls and functions of the common cuckoo (Cuculus canorus, CC). However, there is limited research on the calls and functions of female CCs. In this study, we conducted playback experiments with calls from female CCs, male CCs, and males of the Himalayan cuckoo (C. saturates, CS) as a control group, on actively breeding CCs and their hosts. The results showed that the calls of both male and female CCs attracted CCs and their hosts in the experimental area while the control group did not attract any birds. The attracted CCs were predominantly males. Among the attracted hosts, there were Oriental reed warblers (Acrocephalus orientalis) and black-browed reed warblers (Acrocephalus bistrigiceps). Generalized linear mixed model analysis revealed that the number of individuals attracted by female CC calls was significantly higher than the number attracted by male CC calls, both for male CCs and hosts. Furthermore, male CCs were attracted by male and female CC calls to a significantly greater extent during the incubation stage than during the nestling feeding stage, while there was no difference in the number of attracted host individuals. Our study showed that the calls of female CCs play an important role in the communication between male and female CCs, and hosts are more responsive to the calls of female CCs, suggesting that they perceive female cuckoos as more threatening.